1. Field of the Invention
The present invention relates to an electronically controlled suspension system, more particularly, to a gas suspension system for controlling the body attitude of a vehicle having reserve tanks for holding compressed air which is supplied by a compressor.
2. Description of the Related Art
A well-known electronically controlled suspension system exists in which the gas compressed by a compressor is supplied to a gas spring provided with the suspension so as to control the body attitude of a vehicle. Such a system requires a motor with great capacity to generate enough torque for starting the compressor. Such a motor requires much electric current to be started, which can adversely effect other electric devices of the vehicle, such as lamps or audio equipment.
To solve the aforementioned problem, Japanese Published Unexamined patent application No. 61-43509 discloses a system in which, with the aim of reducing the starting torque of the compressor, the high pressure air compressed by the compressor and held within a high pressure reserve tank is returned to a suction port of the compressor for a preset period following the start-up of the compressor.
Although the starting torque is decreased in this suspension system, the high pressure air from the reserve tank is further compressed during the preset period to deliver the air at higher pressure than necessary because the high pressure of the reserve tank is also applied to the delivery port of the compressor. The decrease in the starting torque by the suspension system is therefore rather small and the air circuit at the delivery port of the compressor has to be constructed to have sufficient rigidity to resist the higher pressure.